import * as THREE from "@/libs/three/lib/three.js";
THREE.GLTFLoader = (function() {
  function GLTFLoader(manager) {
    THREE.Loader.call(this, manager);

    this.dracoLoader = null;
    this.ddsLoader = null;
    this.ktx2Loader = null;
    this.meshoptDecoder = null;

    this.pluginCallbacks = [];

    this.register(function(parser) {
      return new GLTFMaterialsClearcoatExtension(parser);
    });

    this.register(function(parser) {
      return new GLTFTextureBasisUExtension(parser);
    });

    this.register(function(parser) {
      return new GLTFTextureWebPExtension(parser);
    });

    this.register(function(parser) {
      return new GLTFMaterialsTransmissionExtension(parser);
    });

    this.register(function(parser) {
      return new GLTFLightsExtension(parser);
    });

    this.register(function(parser) {
      return new GLTFMeshoptCompression(parser);
    });
  }

  GLTFLoader.prototype = Object.assign(Object.create(THREE.Loader.prototype), {
    constructor: GLTFLoader,

    load: function(url, onLoad, onProgress, onError) {
      var scope = this;

      var resourcePath;

      if (this.resourcePath !== "") {
        resourcePath = this.resourcePath;
      } else if (this.path !== "") {
        resourcePath = this.path;
      } else {
        resourcePath = THREE.LoaderUtils.extractUrlBase(url);
      }

      // Tells the LoadingManager to track an extra item, which resolves after
      // the model is fully loaded. This means the count of items loaded will
      // be incorrect, but ensures manager.onLoad() does not fire early.
      this.manager.itemStart(url);

      var _onError = function(e) {
        if (onError) {
          onError(e);
        } else {
          console.error(e);
        }

        scope.manager.itemError(url);
        scope.manager.itemEnd(url);
      };

      var loader = new THREE.FileLoader(this.manager);

      loader.setPath(this.path);
      loader.setResponseType("arraybuffer");
      loader.setRequestHeader(this.requestHeader);
      loader.setWithCredentials(this.withCredentials);

      loader.load(
        url,
        function(data) {
          try {
            scope.parse(
              data,
              resourcePath,
              function(gltf) {
                onLoad(gltf);

                scope.manager.itemEnd(url);
              },
              _onError
            );
          } catch (e) {
            _onError(e);
          }
        },
        onProgress,
        _onError
      );
    },

    setDRACOLoader: function(dracoLoader) {
      this.dracoLoader = dracoLoader;
      return this;
    },

    setDDSLoader: function(ddsLoader) {
      this.ddsLoader = ddsLoader;
      return this;
    },

    setKTX2Loader: function(ktx2Loader) {
      this.ktx2Loader = ktx2Loader;
      return this;
    },

    setMeshoptDecoder: function(meshoptDecoder) {
      this.meshoptDecoder = meshoptDecoder;
      return this;
    },

    register: function(callback) {
      if (this.pluginCallbacks.indexOf(callback) === -1) {
        this.pluginCallbacks.push(callback);
      }

      return this;
    },

    unregister: function(callback) {
      if (this.pluginCallbacks.indexOf(callback) !== -1) {
        this.pluginCallbacks.splice(this.pluginCallbacks.indexOf(callback), 1);
      }

      return this;
    },

    parse: function(data, path, onLoad, onError) {
      var content;
      var extensions = {};
      var plugins = {};

      if (typeof data === "string") {
        content = data;
      } else {
        var magic = THREE.LoaderUtils.decodeText(new Uint8Array(data, 0, 4));

        if (magic === BINARY_EXTENSION_HEADER_MAGIC) {
          try {
            extensions[EXTENSIONS.KHR_BINARY_GLTF] = new GLTFBinaryExtension(
              data
            );
          } catch (error) {
            if (onError) onError(error);
            return;
          }

          content = extensions[EXTENSIONS.KHR_BINARY_GLTF].content;
        } else {
          content = THREE.LoaderUtils.decodeText(new Uint8Array(data));
        }
      }

      var json = JSON.parse(content);

      if (json.asset === undefined || json.asset.version[0] < 2) {
        if (onError)
          onError(
            new Error(
              "THREE.GLTFLoader: Unsupported asset. glTF versions >=2.0 are supported."
            )
          );
        return;
      }

      var parser = new GLTFParser(json, {
        path: path || this.resourcePath || "",
        crossOrigin: this.crossOrigin,
        manager: this.manager,
        ktx2Loader: this.ktx2Loader,
        meshoptDecoder: this.meshoptDecoder
      });

      parser.fileLoader.setRequestHeader(this.requestHeader);

      for (var i = 0; i < this.pluginCallbacks.length; i++) {
        var plugin = this.pluginCallbacks[i](parser);
        plugins[plugin.name] = plugin;

        // Workaround to avoid determining as unknown extension
        // in addUnknownExtensionsToUserData().
        // Remove this workaround if we move all the existing
        // extension handlers to plugin system
        extensions[plugin.name] = true;
      }

      if (json.extensionsUsed) {
        for (var i = 0; i < json.extensionsUsed.length; ++i) {
          var extensionName = json.extensionsUsed[i];
          var extensionsRequired = json.extensionsRequired || [];

          switch (extensionName) {
            case EXTENSIONS.KHR_MATERIALS_UNLIT:
              extensions[extensionName] = new GLTFMaterialsUnlitExtension();
              break;

            case EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
              extensions[
                extensionName
              ] = new GLTFMaterialsPbrSpecularGlossinessExtension();
              break;

            case EXTENSIONS.KHR_DRACO_MESH_COMPRESSION:
              extensions[extensionName] = new GLTFDracoMeshCompressionExtension(
                json,
                this.dracoLoader
              );
              break;

            case EXTENSIONS.MSFT_TEXTURE_DDS:
              extensions[extensionName] = new GLTFTextureDDSExtension(
                this.ddsLoader
              );
              break;

            case EXTENSIONS.KHR_TEXTURE_TRANSFORM:
              extensions[extensionName] = new GLTFTextureTransformExtension();
              break;

            case EXTENSIONS.KHR_MESH_QUANTIZATION:
              extensions[extensionName] = new GLTFMeshQuantizationExtension();
              break;

            default:
              if (
                extensionsRequired.indexOf(extensionName) >= 0 &&
                plugins[extensionName] === undefined
              ) {
                console.warn(
                  'THREE.GLTFLoader: Unknown extension "' + extensionName + '".'
                );
              }
          }
        }
      }

      parser.setExtensions(extensions);
      parser.setPlugins(plugins);
      parser.parse(onLoad, onError);
    }
  });

  /* GLTFREGISTRY */

  function GLTFRegistry() {
    var objects = {};

    return {
      get: function(key) {
        return objects[key];
      },

      add: function(key, object) {
        objects[key] = object;
      },

      remove: function(key) {
        delete objects[key];
      },

      removeAll: function() {
        objects = {};
      }
    };
  }

  /*********************************/
  /********** EXTENSIONS ***********/
  /*********************************/

  var EXTENSIONS = {
    KHR_BINARY_GLTF: "KHR_binary_glTF",
    KHR_DRACO_MESH_COMPRESSION: "KHR_draco_mesh_compression",
    KHR_LIGHTS_PUNCTUAL: "KHR_lights_punctual",
    KHR_MATERIALS_CLEARCOAT: "KHR_materials_clearcoat",
    KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS:
      "KHR_materials_pbrSpecularGlossiness",
    KHR_MATERIALS_TRANSMISSION: "KHR_materials_transmission",
    KHR_MATERIALS_UNLIT: "KHR_materials_unlit",
    KHR_TEXTURE_BASISU: "KHR_texture_basisu",
    KHR_TEXTURE_TRANSFORM: "KHR_texture_transform",
    KHR_MESH_QUANTIZATION: "KHR_mesh_quantization",
    EXT_TEXTURE_WEBP: "EXT_texture_webp",
    EXT_MESHOPT_COMPRESSION: "EXT_meshopt_compression",
    MSFT_TEXTURE_DDS: "MSFT_texture_dds"
  };

  /**
   * DDS Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/MSFT_texture_dds
   *
   */
  function GLTFTextureDDSExtension(ddsLoader) {
    if (!ddsLoader) {
      throw new Error(
        "THREE.GLTFLoader: Attempting to load .dds texture without importing THREE.DDSLoader"
      );
    }

    this.name = EXTENSIONS.MSFT_TEXTURE_DDS;
    this.ddsLoader = ddsLoader;
  }

  /**
   * Punctual Lights Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_lights_punctual
   */
  function GLTFLightsExtension(parser) {
    this.parser = parser;
    this.name = EXTENSIONS.KHR_LIGHTS_PUNCTUAL;

    // Object3D instance caches
    this.cache = { refs: {}, uses: {} };
  }

  GLTFLightsExtension.prototype._markDefs = function() {
    var parser = this.parser;
    var nodeDefs = this.parser.json.nodes || [];

    for (
      var nodeIndex = 0, nodeLength = nodeDefs.length;
      nodeIndex < nodeLength;
      nodeIndex++
    ) {
      var nodeDef = nodeDefs[nodeIndex];

      if (
        nodeDef.extensions &&
        nodeDef.extensions[this.name] &&
        nodeDef.extensions[this.name].light !== undefined
      ) {
        parser._addNodeRef(this.cache, nodeDef.extensions[this.name].light);
      }
    }
  };

  GLTFLightsExtension.prototype._loadLight = function(lightIndex) {
    var parser = this.parser;
    var cacheKey = "light:" + lightIndex;
    var dependency = parser.cache.get(cacheKey);

    if (dependency) return dependency;

    var json = parser.json;
    var extensions = (json.extensions && json.extensions[this.name]) || {};
    var lightDefs = extensions.lights || [];
    var lightDef = lightDefs[lightIndex];
    var lightNode;

    var color = new THREE.Color(0xffffff);

    if (lightDef.color !== undefined) color.fromArray(lightDef.color);

    var range = lightDef.range !== undefined ? lightDef.range : 0;

    switch (lightDef.type) {
      case "directional":
        lightNode = new THREE.DirectionalLight(color);
        lightNode.target.position.set(0, 0, -1);
        lightNode.add(lightNode.target);
        break;

      case "point":
        lightNode = new THREE.PointLight(color);
        lightNode.distance = range;
        break;

      case "spot":
        lightNode = new THREE.SpotLight(color);
        lightNode.distance = range;
        // Handle spotlight properties.
        lightDef.spot = lightDef.spot || {};
        lightDef.spot.innerConeAngle =
          lightDef.spot.innerConeAngle !== undefined
            ? lightDef.spot.innerConeAngle
            : 0;
        lightDef.spot.outerConeAngle =
          lightDef.spot.outerConeAngle !== undefined
            ? lightDef.spot.outerConeAngle
            : Math.PI / 4.0;
        lightNode.angle = lightDef.spot.outerConeAngle;
        lightNode.penumbra =
          1.0 - lightDef.spot.innerConeAngle / lightDef.spot.outerConeAngle;
        lightNode.target.position.set(0, 0, -1);
        lightNode.add(lightNode.target);
        break;

      default:
        throw new Error(
          "THREE.GLTFLoader: Unexpected light type: " + lightDef.type
        );
    }

    // Some lights (e.g. spot) default to a position other than the origin. Reset the position
    // here, because node-level parsing will only override position if explicitly specified.
    lightNode.position.set(0, 0, 0);

    lightNode.decay = 2;

    if (lightDef.intensity !== undefined)
      lightNode.intensity = lightDef.intensity;

    lightNode.name = parser.createUniqueName(
      lightDef.name || "light_" + lightIndex
    );

    dependency = Promise.resolve(lightNode);

    parser.cache.add(cacheKey, dependency);

    return dependency;
  };

  GLTFLightsExtension.prototype.createNodeAttachment = function(nodeIndex) {
    var self = this;
    var parser = this.parser;
    var json = parser.json;
    var nodeDef = json.nodes[nodeIndex];
    var lightDef = (nodeDef.extensions && nodeDef.extensions[this.name]) || {};
    var lightIndex = lightDef.light;

    if (lightIndex === undefined) return null;

    return this._loadLight(lightIndex).then(function(light) {
      return parser._getNodeRef(self.cache, lightIndex, light);
    });
  };

  /**
   * Unlit Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_unlit
   */
  function GLTFMaterialsUnlitExtension() {
    this.name = EXTENSIONS.KHR_MATERIALS_UNLIT;
  }

  GLTFMaterialsUnlitExtension.prototype.getMaterialType = function() {
    return THREE.MeshBasicMaterial;
  };

  GLTFMaterialsUnlitExtension.prototype.extendParams = function(
    materialParams,
    materialDef,
    parser
  ) {
    var pending = [];

    materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
    materialParams.opacity = 1.0;

    var metallicRoughness = materialDef.pbrMetallicRoughness;

    if (metallicRoughness) {
      if (Array.isArray(metallicRoughness.baseColorFactor)) {
        var array = metallicRoughness.baseColorFactor;

        materialParams.color.fromArray(array);
        materialParams.opacity = array[3];
      }

      if (metallicRoughness.baseColorTexture !== undefined) {
        pending.push(
          parser.assignTexture(
            materialParams,
            "map",
            metallicRoughness.baseColorTexture
          )
        );
      }
    }

    return Promise.all(pending);
  };

  /**
   * Clearcoat Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_clearcoat
   */
  function GLTFMaterialsClearcoatExtension(parser) {
    this.parser = parser;
    this.name = EXTENSIONS.KHR_MATERIALS_CLEARCOAT;
  }

  GLTFMaterialsClearcoatExtension.prototype.getMaterialType = function(
    materialIndex
  ) {
    var parser = this.parser;
    var materialDef = parser.json.materials[materialIndex];

    if (!materialDef.extensions || !materialDef.extensions[this.name])
      return null;

    return THREE.MeshPhysicalMaterial;
  };

  GLTFMaterialsClearcoatExtension.prototype.extendMaterialParams = function(
    materialIndex,
    materialParams
  ) {
    var parser = this.parser;
    var materialDef = parser.json.materials[materialIndex];

    if (!materialDef.extensions || !materialDef.extensions[this.name]) {
      return Promise.resolve();
    }

    var pending = [];

    var extension = materialDef.extensions[this.name];

    if (extension.clearcoatFactor !== undefined) {
      materialParams.clearcoat = extension.clearcoatFactor;
    }

    if (extension.clearcoatTexture !== undefined) {
      pending.push(
        parser.assignTexture(
          materialParams,
          "clearcoatMap",
          extension.clearcoatTexture
        )
      );
    }

    if (extension.clearcoatRoughnessFactor !== undefined) {
      materialParams.clearcoatRoughness = extension.clearcoatRoughnessFactor;
    }

    if (extension.clearcoatRoughnessTexture !== undefined) {
      pending.push(
        parser.assignTexture(
          materialParams,
          "clearcoatRoughnessMap",
          extension.clearcoatRoughnessTexture
        )
      );
    }

    if (extension.clearcoatNormalTexture !== undefined) {
      pending.push(
        parser.assignTexture(
          materialParams,
          "clearcoatNormalMap",
          extension.clearcoatNormalTexture
        )
      );

      if (extension.clearcoatNormalTexture.scale !== undefined) {
        var scale = extension.clearcoatNormalTexture.scale;

        // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
        materialParams.clearcoatNormalScale = new THREE.Vector2(scale, -scale);
      }
    }

    return Promise.all(pending);
  };

  /**
   * Transmission Materials Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_transmission
   * Draft: https://github.com/KhronosGroup/glTF/pull/1698
   */
  function GLTFMaterialsTransmissionExtension(parser) {
    this.parser = parser;
    this.name = EXTENSIONS.KHR_MATERIALS_TRANSMISSION;
  }

  GLTFMaterialsTransmissionExtension.prototype.getMaterialType = function(
    materialIndex
  ) {
    var parser = this.parser;
    var materialDef = parser.json.materials[materialIndex];

    if (!materialDef.extensions || !materialDef.extensions[this.name])
      return null;

    return THREE.MeshPhysicalMaterial;
  };

  GLTFMaterialsTransmissionExtension.prototype.extendMaterialParams = function(
    materialIndex,
    materialParams
  ) {
    var parser = this.parser;
    var materialDef = parser.json.materials[materialIndex];

    if (!materialDef.extensions || !materialDef.extensions[this.name]) {
      return Promise.resolve();
    }

    var pending = [];

    var extension = materialDef.extensions[this.name];

    if (extension.transmissionFactor !== undefined) {
      materialParams.transmission = extension.transmissionFactor;
    }

    if (extension.transmissionTexture !== undefined) {
      pending.push(
        parser.assignTexture(
          materialParams,
          "transmissionMap",
          extension.transmissionTexture
        )
      );
    }

    return Promise.all(pending);
  };

  /**
   * BasisU Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_basisu
   */
  function GLTFTextureBasisUExtension(parser) {
    this.parser = parser;
    this.name = EXTENSIONS.KHR_TEXTURE_BASISU;
  }

  GLTFTextureBasisUExtension.prototype.loadTexture = function(textureIndex) {
    var parser = this.parser;
    var json = parser.json;

    var textureDef = json.textures[textureIndex];

    if (!textureDef.extensions || !textureDef.extensions[this.name]) {
      return null;
    }

    var extension = textureDef.extensions[this.name];
    var source = json.images[extension.source];
    var loader = parser.options.ktx2Loader;

    if (!loader) {
      if (
        json.extensionsRequired &&
        json.extensionsRequired.indexOf(this.name) >= 0
      ) {
        throw new Error(
          "THREE.GLTFLoader: setKTX2Loader must be called before loading KTX2 textures"
        );
      } else {
        // Assumes that the extension is optional and that a fallback texture is present
        return null;
      }
    }

    return parser.loadTextureImage(textureIndex, source, loader);
  };

  /**
   * WebP Texture Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_texture_webp
   */
  function GLTFTextureWebPExtension(parser) {
    this.parser = parser;
    this.name = EXTENSIONS.EXT_TEXTURE_WEBP;
    this.isSupported = null;
  }

  GLTFTextureWebPExtension.prototype.loadTexture = function(textureIndex) {
    var name = this.name;
    var parser = this.parser;
    var json = parser.json;

    var textureDef = json.textures[textureIndex];

    if (!textureDef.extensions || !textureDef.extensions[name]) {
      return null;
    }

    var extension = textureDef.extensions[name];
    var source = json.images[extension.source];
    var loader = source.uri
      ? parser.options.manager.getHandler(source.uri)
      : parser.textureLoader;

    return this.detectSupport().then(function(isSupported) {
      if (isSupported)
        return parser.loadTextureImage(textureIndex, source, loader);

      if (
        json.extensionsRequired &&
        json.extensionsRequired.indexOf(name) >= 0
      ) {
        throw new Error(
          "THREE.GLTFLoader: WebP required by asset but unsupported."
        );
      }

      // Fall back to PNG or JPEG.
      return parser.loadTexture(textureIndex);
    });
  };

  GLTFTextureWebPExtension.prototype.detectSupport = function() {
    if (!this.isSupported) {
      this.isSupported = new Promise(function(resolve) {
        var image = new Image();

        // Lossy test image. Support for lossy images doesn't guarantee support for all
        // WebP images, unfortunately.
        image.src =
          "";

        image.onload = image.onerror = function() {
          resolve(image.height === 1);
        };
      });
    }

    return this.isSupported;
  };

  /**
   * meshopt BufferView Compression Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Vendor/EXT_meshopt_compression
   */
  function GLTFMeshoptCompression(parser) {
    this.name = EXTENSIONS.EXT_MESHOPT_COMPRESSION;
    this.parser = parser;
  }

  GLTFMeshoptCompression.prototype.loadBufferView = function(index) {
    var json = this.parser.json;
    var bufferView = json.bufferViews[index];

    if (bufferView.extensions && bufferView.extensions[this.name]) {
      var extensionDef = bufferView.extensions[this.name];

      var buffer = this.parser.getDependency("buffer", extensionDef.buffer);
      var decoder = this.parser.options.meshoptDecoder;

      if (!decoder || !decoder.supported) {
        if (
          json.extensionsRequired &&
          json.extensionsRequired.indexOf(this.name) >= 0
        ) {
          throw new Error(
            "THREE.GLTFLoader: setMeshoptDecoder must be called before loading compressed files"
          );
        } else {
          // Assumes that the extension is optional and that fallback buffer data is present
          return null;
        }
      }

      return Promise.all([buffer, decoder.ready]).then(function(res) {
        var byteOffset = extensionDef.byteOffset || 0;
        var byteLength = extensionDef.byteLength || 0;

        var count = extensionDef.count;
        var stride = extensionDef.byteStride;

        var result = new ArrayBuffer(count * stride);
        var source = new Uint8Array(res[0], byteOffset, byteLength);

        decoder.decodeGltfBuffer(
          new Uint8Array(result),
          count,
          stride,
          source,
          extensionDef.mode,
          extensionDef.filter
        );
        return result;
      });
    } else {
      return null;
    }
  };

  /* BINARY EXTENSION */
  var BINARY_EXTENSION_HEADER_MAGIC = "glTF";
  var BINARY_EXTENSION_HEADER_LENGTH = 12;
  var BINARY_EXTENSION_CHUNK_TYPES = { JSON: 0x4e4f534a, BIN: 0x004e4942 };

  function GLTFBinaryExtension(data) {
    this.name = EXTENSIONS.KHR_BINARY_GLTF;
    this.content = null;
    this.body = null;

    var headerView = new DataView(data, 0, BINARY_EXTENSION_HEADER_LENGTH);

    this.header = {
      magic: THREE.LoaderUtils.decodeText(new Uint8Array(data.slice(0, 4))),
      version: headerView.getUint32(4, true),
      length: headerView.getUint32(8, true)
    };

    if (this.header.magic !== BINARY_EXTENSION_HEADER_MAGIC) {
      throw new Error("THREE.GLTFLoader: Unsupported glTF-Binary header.");
    } else if (this.header.version < 2.0) {
      throw new Error("THREE.GLTFLoader: Legacy binary file detected.");
    }

    var chunkContentsLength =
      this.header.length - BINARY_EXTENSION_HEADER_LENGTH;
    var chunkView = new DataView(data, BINARY_EXTENSION_HEADER_LENGTH);
    var chunkIndex = 0;

    while (chunkIndex < chunkContentsLength) {
      var chunkLength = chunkView.getUint32(chunkIndex, true);
      chunkIndex += 4;

      var chunkType = chunkView.getUint32(chunkIndex, true);
      chunkIndex += 4;

      if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.JSON) {
        var contentArray = new Uint8Array(
          data,
          BINARY_EXTENSION_HEADER_LENGTH + chunkIndex,
          chunkLength
        );
        this.content = THREE.LoaderUtils.decodeText(contentArray);
      } else if (chunkType === BINARY_EXTENSION_CHUNK_TYPES.BIN) {
        var byteOffset = BINARY_EXTENSION_HEADER_LENGTH + chunkIndex;
        this.body = data.slice(byteOffset, byteOffset + chunkLength);
      }

      // Clients must ignore chunks with unknown types.

      chunkIndex += chunkLength;
    }

    if (this.content === null) {
      throw new Error("THREE.GLTFLoader: JSON content not found.");
    }
  }

  /**
   * DRACO Mesh Compression Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_draco_mesh_compression
   */
  function GLTFDracoMeshCompressionExtension(json, dracoLoader) {
    if (!dracoLoader) {
      throw new Error("THREE.GLTFLoader: No DRACOLoader instance provided.");
    }

    this.name = EXTENSIONS.KHR_DRACO_MESH_COMPRESSION;
    this.json = json;
    this.dracoLoader = dracoLoader;
    this.dracoLoader.preload();
  }

  GLTFDracoMeshCompressionExtension.prototype.decodePrimitive = function(
    primitive,
    parser
  ) {
    var json = this.json;
    var dracoLoader = this.dracoLoader;
    var bufferViewIndex = primitive.extensions[this.name].bufferView;
    var gltfAttributeMap = primitive.extensions[this.name].attributes;
    var threeAttributeMap = {};
    var attributeNormalizedMap = {};
    var attributeTypeMap = {};

    for (var attributeName in gltfAttributeMap) {
      var threeAttributeName =
        ATTRIBUTES[attributeName] || attributeName.toLowerCase();

      threeAttributeMap[threeAttributeName] = gltfAttributeMap[attributeName];
    }

    for (attributeName in primitive.attributes) {
      var threeAttributeName =
        ATTRIBUTES[attributeName] || attributeName.toLowerCase();

      if (gltfAttributeMap[attributeName] !== undefined) {
        var accessorDef = json.accessors[primitive.attributes[attributeName]];
        var componentType = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

        attributeTypeMap[threeAttributeName] = componentType;
        attributeNormalizedMap[threeAttributeName] =
          accessorDef.normalized === true;
      }
    }

    return parser
      .getDependency("bufferView", bufferViewIndex)
      .then(function(bufferView) {
        return new Promise(function(resolve) {
          dracoLoader.decodeDracoFile(
            bufferView,
            function(geometry) {
              for (var attributeName in geometry.attributes) {
                var attribute = geometry.attributes[attributeName];
                var normalized = attributeNormalizedMap[attributeName];

                if (normalized !== undefined) attribute.normalized = normalized;
              }

              resolve(geometry);
            },
            threeAttributeMap,
            attributeTypeMap
          );
        });
      });
  };

  /**
   * Texture Transform Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_texture_transform
   */
  function GLTFTextureTransformExtension() {
    this.name = EXTENSIONS.KHR_TEXTURE_TRANSFORM;
  }

  GLTFTextureTransformExtension.prototype.extendTexture = function(
    texture,
    transform
  ) {
    texture = texture.clone();

    if (transform.offset !== undefined) {
      texture.offset.fromArray(transform.offset);
    }

    if (transform.rotation !== undefined) {
      texture.rotation = transform.rotation;
    }

    if (transform.scale !== undefined) {
      texture.repeat.fromArray(transform.scale);
    }

    if (transform.texCoord !== undefined) {
      console.warn(
        'THREE.GLTFLoader: Custom UV sets in "' +
          this.name +
          '" extension not yet supported.'
      );
    }

    texture.needsUpdate = true;

    return texture;
  };

  /**
   * Specular-Glossiness Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_materials_pbrSpecularGlossiness
   */

  /**
   * A sub class of THREE.StandardMaterial with some of the functionality
   * changed via the `onBeforeCompile` callback
   * @pailhead
   */

  function GLTFMeshStandardSGMaterial(params) {
    THREE.MeshStandardMaterial.call(this);

    this.isGLTFSpecularGlossinessMaterial = true;

    //various chunks that need replacing
    var specularMapParsFragmentChunk = [
      "#ifdef USE_SPECULARMAP",
      "	uniform sampler2D specularMap;",
      "#endif"
    ].join("\n");

    var glossinessMapParsFragmentChunk = [
      "#ifdef USE_GLOSSINESSMAP",
      "	uniform sampler2D glossinessMap;",
      "#endif"
    ].join("\n");

    var specularMapFragmentChunk = [
      "vec3 specularFactor = specular;",
      "#ifdef USE_SPECULARMAP",
      "	vec4 texelSpecular = texture2D( specularMap, vUv );",
      "	texelSpecular = sRGBToLinear( texelSpecular );",
      "	// reads channel RGB, compatible with a glTF Specular-Glossiness (RGBA) texture",
      "	specularFactor *= texelSpecular.rgb;",
      "#endif"
    ].join("\n");

    var glossinessMapFragmentChunk = [
      "float glossinessFactor = glossiness;",
      "#ifdef USE_GLOSSINESSMAP",
      "	vec4 texelGlossiness = texture2D( glossinessMap, vUv );",
      "	// reads channel A, compatible with a glTF Specular-Glossiness (RGBA) texture",
      "	glossinessFactor *= texelGlossiness.a;",
      "#endif"
    ].join("\n");

    var lightPhysicalFragmentChunk = [
      "PhysicalMaterial material;",
      "material.diffuseColor = diffuseColor.rgb * ( 1. - max( specularFactor.r, max( specularFactor.g, specularFactor.b ) ) );",
      "vec3 dxy = max( abs( dFdx( geometryNormal ) ), abs( dFdy( geometryNormal ) ) );",
      "float geometryRoughness = max( max( dxy.x, dxy.y ), dxy.z );",
      "material.specularRoughness = max( 1.0 - glossinessFactor, 0.0525 ); // 0.0525 corresponds to the base mip of a 256 cubemap.",
      "material.specularRoughness += geometryRoughness;",
      "material.specularRoughness = min( material.specularRoughness, 1.0 );",
      "material.specularColor = specularFactor;"
    ].join("\n");

    var uniforms = {
      specular: { value: new THREE.Color().setHex(0xffffff) },
      glossiness: { value: 1 },
      specularMap: { value: null },
      glossinessMap: { value: null }
    };

    this._extraUniforms = uniforms;

    this.onBeforeCompile = function(shader) {
      for (var uniformName in uniforms) {
        shader.uniforms[uniformName] = uniforms[uniformName];
      }

      shader.fragmentShader = shader.fragmentShader
        .replace("uniform float roughness;", "uniform vec3 specular;")
        .replace("uniform float metalness;", "uniform float glossiness;")
        .replace(
          "#include <roughnessmap_pars_fragment>",
          specularMapParsFragmentChunk
        )
        .replace(
          "#include <metalnessmap_pars_fragment>",
          glossinessMapParsFragmentChunk
        )
        .replace("#include <roughnessmap_fragment>", specularMapFragmentChunk)
        .replace("#include <metalnessmap_fragment>", glossinessMapFragmentChunk)
        .replace(
          "#include <lights_physical_fragment>",
          lightPhysicalFragmentChunk
        );
    };

    Object.defineProperties(this, {
      specular: {
        get: function() {
          return uniforms.specular.value;
        },
        set: function(v) {
          uniforms.specular.value = v;
        }
      },

      specularMap: {
        get: function() {
          return uniforms.specularMap.value;
        },
        set: function(v) {
          uniforms.specularMap.value = v;

          if (v) {
            this.defines.USE_SPECULARMAP = ""; // USE_UV is set by the renderer for specular maps
          } else {
            delete this.defines.USE_SPECULARMAP;
          }
        }
      },

      glossiness: {
        get: function() {
          return uniforms.glossiness.value;
        },
        set: function(v) {
          uniforms.glossiness.value = v;
        }
      },

      glossinessMap: {
        get: function() {
          return uniforms.glossinessMap.value;
        },
        set: function(v) {
          uniforms.glossinessMap.value = v;

          if (v) {
            this.defines.USE_GLOSSINESSMAP = "";
            this.defines.USE_UV = "";
          } else {
            delete this.defines.USE_GLOSSINESSMAP;
            delete this.defines.USE_UV;
          }
        }
      }
    });

    delete this.metalness;
    delete this.roughness;
    delete this.metalnessMap;
    delete this.roughnessMap;

    this.setValues(params);
  }

  GLTFMeshStandardSGMaterial.prototype = Object.create(
    THREE.MeshStandardMaterial.prototype
  );
  GLTFMeshStandardSGMaterial.prototype.constructor = GLTFMeshStandardSGMaterial;

  GLTFMeshStandardSGMaterial.prototype.copy = function(source) {
    THREE.MeshStandardMaterial.prototype.copy.call(this, source);
    this.specularMap = source.specularMap;
    this.specular.copy(source.specular);
    this.glossinessMap = source.glossinessMap;
    this.glossiness = source.glossiness;
    delete this.metalness;
    delete this.roughness;
    delete this.metalnessMap;
    delete this.roughnessMap;
    return this;
  };

  function GLTFMaterialsPbrSpecularGlossinessExtension() {
    return {
      name: EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS,

      specularGlossinessParams: [
        "color",
        "map",
        "lightMap",
        "lightMapIntensity",
        "aoMap",
        "aoMapIntensity",
        "emissive",
        "emissiveIntensity",
        "emissiveMap",
        "bumpMap",
        "bumpScale",
        "normalMap",
        "normalMapType",
        "displacementMap",
        "displacementScale",
        "displacementBias",
        "specularMap",
        "specular",
        "glossinessMap",
        "glossiness",
        "alphaMap",
        "envMap",
        "envMapIntensity",
        "refractionRatio"
      ],

      getMaterialType: function() {
        return GLTFMeshStandardSGMaterial;
      },

      extendParams: function(materialParams, materialDef, parser) {
        var pbrSpecularGlossiness = materialDef.extensions[this.name];

        materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
        materialParams.opacity = 1.0;

        var pending = [];

        if (Array.isArray(pbrSpecularGlossiness.diffuseFactor)) {
          var array = pbrSpecularGlossiness.diffuseFactor;

          materialParams.color.fromArray(array);
          materialParams.opacity = array[3];
        }

        if (pbrSpecularGlossiness.diffuseTexture !== undefined) {
          pending.push(
            parser.assignTexture(
              materialParams,
              "map",
              pbrSpecularGlossiness.diffuseTexture
            )
          );
        }

        materialParams.emissive = new THREE.Color(0.0, 0.0, 0.0);
        materialParams.glossiness =
          pbrSpecularGlossiness.glossinessFactor !== undefined
            ? pbrSpecularGlossiness.glossinessFactor
            : 1.0;
        materialParams.specular = new THREE.Color(1.0, 1.0, 1.0);

        if (Array.isArray(pbrSpecularGlossiness.specularFactor)) {
          materialParams.specular.fromArray(
            pbrSpecularGlossiness.specularFactor
          );
        }

        if (pbrSpecularGlossiness.specularGlossinessTexture !== undefined) {
          var specGlossMapDef = pbrSpecularGlossiness.specularGlossinessTexture;
          pending.push(
            parser.assignTexture(
              materialParams,
              "glossinessMap",
              specGlossMapDef
            )
          );
          pending.push(
            parser.assignTexture(materialParams, "specularMap", specGlossMapDef)
          );
        }

        return Promise.all(pending);
      },

      createMaterial: function(materialParams) {
        var material = new GLTFMeshStandardSGMaterial(materialParams);
        material.fog = true;

        material.color = materialParams.color;

        material.map =
          materialParams.map === undefined ? null : materialParams.map;

        material.lightMap = null;
        material.lightMapIntensity = 1.0;

        material.aoMap =
          materialParams.aoMap === undefined ? null : materialParams.aoMap;
        material.aoMapIntensity = 1.0;

        material.emissive = materialParams.emissive;
        material.emissiveIntensity = 1.0;
        material.emissiveMap =
          materialParams.emissiveMap === undefined
            ? null
            : materialParams.emissiveMap;

        material.bumpMap =
          materialParams.bumpMap === undefined ? null : materialParams.bumpMap;
        material.bumpScale = 1;

        material.normalMap =
          materialParams.normalMap === undefined
            ? null
            : materialParams.normalMap;
        material.normalMapType = THREE.TangentSpaceNormalMap;

        if (materialParams.normalScale)
          material.normalScale = materialParams.normalScale;

        material.displacementMap = null;
        material.displacementScale = 1;
        material.displacementBias = 0;

        material.specularMap =
          materialParams.specularMap === undefined
            ? null
            : materialParams.specularMap;
        material.specular = materialParams.specular;

        material.glossinessMap =
          materialParams.glossinessMap === undefined
            ? null
            : materialParams.glossinessMap;
        material.glossiness = materialParams.glossiness;

        material.alphaMap = null;

        material.envMap =
          materialParams.envMap === undefined ? null : materialParams.envMap;
        material.envMapIntensity = 1.0;

        material.refractionRatio = 0.98;

        return material;
      }
    };
  }

  /**
   * Mesh Quantization Extension
   *
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/extensions/2.0/Khronos/KHR_mesh_quantization
   */
  function GLTFMeshQuantizationExtension() {
    this.name = EXTENSIONS.KHR_MESH_QUANTIZATION;
  }

  /*********************************/
  /********** INTERPOLATION ********/
  /*********************************/

  // Spline Interpolation
  // Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#appendix-c-spline-interpolation
  function GLTFCubicSplineInterpolant(
    parameterPositions,
    sampleValues,
    sampleSize,
    resultBuffer
  ) {
    THREE.Interpolant.call(
      this,
      parameterPositions,
      sampleValues,
      sampleSize,
      resultBuffer
    );
  }

  GLTFCubicSplineInterpolant.prototype = Object.create(
    THREE.Interpolant.prototype
  );
  GLTFCubicSplineInterpolant.prototype.constructor = GLTFCubicSplineInterpolant;

  GLTFCubicSplineInterpolant.prototype.copySampleValue_ = function(index) {
    // Copies a sample value to the result buffer. See description of glTF
    // CUBICSPLINE values layout in interpolate_() function below.

    var result = this.resultBuffer,
      values = this.sampleValues,
      valueSize = this.valueSize,
      offset = index * valueSize * 3 + valueSize;

    for (var i = 0; i !== valueSize; i++) {
      result[i] = values[offset + i];
    }

    return result;
  };

  GLTFCubicSplineInterpolant.prototype.beforeStart_ =
    GLTFCubicSplineInterpolant.prototype.copySampleValue_;

  GLTFCubicSplineInterpolant.prototype.afterEnd_ =
    GLTFCubicSplineInterpolant.prototype.copySampleValue_;

  GLTFCubicSplineInterpolant.prototype.interpolate_ = function(i1, t0, t, t1) {
    var result = this.resultBuffer;
    var values = this.sampleValues;
    var stride = this.valueSize;

    var stride2 = stride * 2;
    var stride3 = stride * 3;

    var td = t1 - t0;

    var p = (t - t0) / td;
    var pp = p * p;
    var ppp = pp * p;

    var offset1 = i1 * stride3;
    var offset0 = offset1 - stride3;

    var s2 = -2 * ppp + 3 * pp;
    var s3 = ppp - pp;
    var s0 = 1 - s2;
    var s1 = s3 - pp + p;

    // Layout of keyframe output values for CUBICSPLINE animations:
    //   [ inTangent_1, splineVertex_1, outTangent_1, inTangent_2, splineVertex_2, ... ]
    for (var i = 0; i !== stride; i++) {
      var p0 = values[offset0 + i + stride]; // splineVertex_k
      var m0 = values[offset0 + i + stride2] * td; // outTangent_k * (t_k+1 - t_k)
      var p1 = values[offset1 + i + stride]; // splineVertex_k+1
      var m1 = values[offset1 + i] * td; // inTangent_k+1 * (t_k+1 - t_k)

      result[i] = s0 * p0 + s1 * m0 + s2 * p1 + s3 * m1;
    }

    return result;
  };

  /*********************************/
  /********** INTERNALS ************/
  /*********************************/

  /* CONSTANTS */

  var WEBGL_CONSTANTS = {
    FLOAT: 5126,
    //FLOAT_MAT2: 35674,
    FLOAT_MAT3: 35675,
    FLOAT_MAT4: 35676,
    FLOAT_VEC2: 35664,
    FLOAT_VEC3: 35665,
    FLOAT_VEC4: 35666,
    LINEAR: 9729,
    REPEAT: 10497,
    SAMPLER_2D: 35678,
    POINTS: 0,
    LINES: 1,
    LINE_LOOP: 2,
    LINE_STRIP: 3,
    TRIANGLES: 4,
    TRIANGLE_STRIP: 5,
    TRIANGLE_FAN: 6,
    UNSIGNED_BYTE: 5121,
    UNSIGNED_SHORT: 5123
  };

  var WEBGL_COMPONENT_TYPES = {
    5120: Int8Array,
    5121: Uint8Array,
    5122: Int16Array,
    5123: Uint16Array,
    5125: Uint32Array,
    5126: Float32Array
  };

  var WEBGL_FILTERS = {
    9728: THREE.NearestFilter,
    9729: THREE.LinearFilter,
    9984: THREE.NearestMipmapNearestFilter,
    9985: THREE.LinearMipmapNearestFilter,
    9986: THREE.NearestMipmapLinearFilter,
    9987: THREE.LinearMipmapLinearFilter
  };

  var WEBGL_WRAPPINGS = {
    33071: THREE.ClampToEdgeWrapping,
    33648: THREE.MirroredRepeatWrapping,
    10497: THREE.RepeatWrapping
  };

  var WEBGL_TYPE_SIZES = {
    SCALAR: 1,
    VEC2: 2,
    VEC3: 3,
    VEC4: 4,
    MAT2: 4,
    MAT3: 9,
    MAT4: 16
  };

  var ATTRIBUTES = {
    POSITION: "position",
    NORMAL: "normal",
    TANGENT: "tangent",
    TEXCOORD_0: "uv",
    TEXCOORD_1: "uv2",
    COLOR_0: "color",
    WEIGHTS_0: "skinWeight",
    JOINTS_0: "skinIndex"
  };

  var PATH_PROPERTIES = {
    scale: "scale",
    translation: "position",
    rotation: "quaternion",
    weights: "morphTargetInfluences"
  };

  var INTERPOLATION = {
    CUBICSPLINE: undefined, // We use a custom interpolant (GLTFCubicSplineInterpolation) for CUBICSPLINE tracks. Each
    // keyframe track will be initialized with a default interpolation type, then modified.
    LINEAR: THREE.InterpolateLinear,
    STEP: THREE.InterpolateDiscrete
  };

  var ALPHA_MODES = {
    OPAQUE: "OPAQUE",
    MASK: "MASK",
    BLEND: "BLEND"
  };

  /* UTILITY FUNCTIONS */

  function resolveURL(url, path) {
    // Invalid URL
    if (typeof url !== "string" || url === "") return "";

    // Host Relative URL
    if (/^https?:\/\//i.test(path) && /^\//.test(url)) {
      path = path.replace(/(^https?:\/\/[^\/]+).*/i, "$1");
    }

    // Absolute URL http://,https://,//
    if (/^(https?:)?\/\//i.test(url)) return url;

    // Data URI
    if (/^data:.*,.*$/i.test(url)) return url;

    // Blob URL
    if (/^blob:.*$/i.test(url)) return url;

    // Relative URL
    return path + url;
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material
   */
  function createDefaultMaterial(cache) {
    if (cache["DefaultMaterial"] === undefined) {
      cache["DefaultMaterial"] = new THREE.MeshStandardMaterial({
        color: 0xffffff,
        emissive: 0x000000,
        metalness: 1,
        roughness: 1,
        transparent: false,
        depthTest: true,
        side: THREE.FrontSide
      });
    }

    return cache["DefaultMaterial"];
  }

  function addUnknownExtensionsToUserData(knownExtensions, object, objectDef) {
    // Add unknown glTF extensions to an object's userData.

    for (var name in objectDef.extensions) {
      if (knownExtensions[name] === undefined) {
        object.userData.gltfExtensions = object.userData.gltfExtensions || {};
        object.userData.gltfExtensions[name] = objectDef.extensions[name];
      }
    }
  }

  /**
   * @param {THREE.Object3D|THREE.Material|THREE.BufferGeometry} object
   * @param {GLTF.definition} gltfDef
   */
  function assignExtrasToUserData(object, gltfDef) {
    if (gltfDef.extras !== undefined) {
      if (typeof gltfDef.extras === "object") {
        Object.assign(object.userData, gltfDef.extras);
      } else {
        console.warn(
          "THREE.GLTFLoader: Ignoring primitive type .extras, " + gltfDef.extras
        );
      }
    }
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#morph-targets
   *
   * @param {THREE.BufferGeometry} geometry
   * @param {Array<GLTF.Target>} targets
   * @param {GLTFParser} parser
   * @return {Promise<THREE.BufferGeometry>}
   */
  function addMorphTargets(geometry, targets, parser) {
    var hasMorphPosition = false;
    var hasMorphNormal = false;

    for (var i = 0, il = targets.length; i < il; i++) {
      var target = targets[i];

      if (target.POSITION !== undefined) hasMorphPosition = true;
      if (target.NORMAL !== undefined) hasMorphNormal = true;

      if (hasMorphPosition && hasMorphNormal) break;
    }

    if (!hasMorphPosition && !hasMorphNormal) return Promise.resolve(geometry);

    var pendingPositionAccessors = [];
    var pendingNormalAccessors = [];

    for (var i = 0, il = targets.length; i < il; i++) {
      var target = targets[i];

      if (hasMorphPosition) {
        var pendingAccessor =
          target.POSITION !== undefined
            ? parser.getDependency("accessor", target.POSITION)
            : geometry.attributes.position;

        pendingPositionAccessors.push(pendingAccessor);
      }

      if (hasMorphNormal) {
        var pendingAccessor =
          target.NORMAL !== undefined
            ? parser.getDependency("accessor", target.NORMAL)
            : geometry.attributes.normal;

        pendingNormalAccessors.push(pendingAccessor);
      }
    }

    return Promise.all([
      Promise.all(pendingPositionAccessors),
      Promise.all(pendingNormalAccessors)
    ]).then(function(accessors) {
      var morphPositions = accessors[0];
      var morphNormals = accessors[1];

      if (hasMorphPosition) geometry.morphAttributes.position = morphPositions;
      if (hasMorphNormal) geometry.morphAttributes.normal = morphNormals;
      geometry.morphTargetsRelative = true;

      return geometry;
    });
  }

  /**
   * @param {THREE.Mesh} mesh
   * @param {GLTF.Mesh} meshDef
   */
  function updateMorphTargets(mesh, meshDef) {
    mesh.updateMorphTargets();

    if (meshDef.weights !== undefined) {
      for (var i = 0, il = meshDef.weights.length; i < il; i++) {
        mesh.morphTargetInfluences[i] = meshDef.weights[i];
      }
    }

    // .extras has user-defined data, so check that .extras.targetNames is an array.
    if (meshDef.extras && Array.isArray(meshDef.extras.targetNames)) {
      var targetNames = meshDef.extras.targetNames;

      if (mesh.morphTargetInfluences.length === targetNames.length) {
        mesh.morphTargetDictionary = {};

        for (var i = 0, il = targetNames.length; i < il; i++) {
          mesh.morphTargetDictionary[targetNames[i]] = i;
        }
      } else {
        console.warn(
          "THREE.GLTFLoader: Invalid extras.targetNames length. Ignoring names."
        );
      }
    }
  }

  function createPrimitiveKey(primitiveDef) {
    var dracoExtension =
      primitiveDef.extensions &&
      primitiveDef.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION];
    var geometryKey;

    if (dracoExtension) {
      geometryKey =
        "draco:" +
        dracoExtension.bufferView +
        ":" +
        dracoExtension.indices +
        ":" +
        createAttributesKey(dracoExtension.attributes);
    } else {
      geometryKey =
        primitiveDef.indices +
        ":" +
        createAttributesKey(primitiveDef.attributes) +
        ":" +
        primitiveDef.mode;
    }

    return geometryKey;
  }

  function createAttributesKey(attributes) {
    var attributesKey = "";

    var keys = Object.keys(attributes).sort();

    for (var i = 0, il = keys.length; i < il; i++) {
      attributesKey += keys[i] + ":" + attributes[keys[i]] + ";";
    }

    return attributesKey;
  }

  /* GLTF PARSER */

  function GLTFParser(json, options) {
    this.json = json || {};
    this.extensions = {};
    this.plugins = {};
    this.options = options || {};

    // loader object cache
    this.cache = new GLTFRegistry();

    // associations between Three.js objects and glTF elements
    this.associations = new Map();

    // BufferGeometry caching
    this.primitiveCache = {};

    // Object3D instance caches
    this.meshCache = { refs: {}, uses: {} };
    this.cameraCache = { refs: {}, uses: {} };
    this.lightCache = { refs: {}, uses: {} };

    // Track node names, to ensure no duplicates
    this.nodeNamesUsed = {};

    // Use an ImageBitmapLoader if imageBitmaps are supported. Moves much of the
    // expensive work of uploading a texture to the GPU off the main thread.
    if (
      typeof createImageBitmap !== "undefined" &&
      /Firefox/.test(navigator.userAgent) === false
    ) {
      this.textureLoader = new THREE.ImageBitmapLoader(this.options.manager);
    } else {
      this.textureLoader = new THREE.TextureLoader(this.options.manager);
    }

    this.textureLoader.setCrossOrigin(this.options.crossOrigin);

    this.fileLoader = new THREE.FileLoader(this.options.manager);
    this.fileLoader.setResponseType("arraybuffer");

    if (this.options.crossOrigin === "use-credentials") {
      this.fileLoader.setWithCredentials(true);
    }
  }

  GLTFParser.prototype.setExtensions = function(extensions) {
    this.extensions = extensions;
  };

  GLTFParser.prototype.setPlugins = function(plugins) {
    this.plugins = plugins;
  };

  GLTFParser.prototype.parse = function(onLoad, onError) {
    var parser = this;
    var json = this.json;
    var extensions = this.extensions;

    // Clear the loader cache
    this.cache.removeAll();

    // Mark the special nodes/meshes in json for efficient parse
    this._invokeAll(function(ext) {
      return ext._markDefs && ext._markDefs();
    });

    Promise.all([
      this.getDependencies("scene"),
      this.getDependencies("animation"),
      this.getDependencies("camera")
    ])
      .then(function(dependencies) {
        var result = {
          scene: dependencies[0][json.scene || 0],
          scenes: dependencies[0],
          animations: dependencies[1],
          cameras: dependencies[2],
          asset: json.asset,
          parser: parser,
          userData: {}
        };

        addUnknownExtensionsToUserData(extensions, result, json);

        assignExtrasToUserData(result, json);

        onLoad(result);
      })
      .catch(onError);
  };

  /**
   * Marks the special nodes/meshes in json for efficient parse.
   */
  GLTFParser.prototype._markDefs = function() {
    var nodeDefs = this.json.nodes || [];
    var skinDefs = this.json.skins || [];
    var meshDefs = this.json.meshes || [];

    // Nothing in the node definition indicates whether it is a Bone or an
    // Object3D. Use the skins' joint references to mark bones.
    for (
      var skinIndex = 0, skinLength = skinDefs.length;
      skinIndex < skinLength;
      skinIndex++
    ) {
      var joints = skinDefs[skinIndex].joints;

      for (var i = 0, il = joints.length; i < il; i++) {
        nodeDefs[joints[i]].isBone = true;
      }
    }

    // Iterate over all nodes, marking references to shared resources,
    // as well as skeleton joints.
    for (
      var nodeIndex = 0, nodeLength = nodeDefs.length;
      nodeIndex < nodeLength;
      nodeIndex++
    ) {
      var nodeDef = nodeDefs[nodeIndex];

      if (nodeDef.mesh !== undefined) {
        this._addNodeRef(this.meshCache, nodeDef.mesh);

        // Nothing in the mesh definition indicates whether it is
        // a SkinnedMesh or Mesh. Use the node's mesh reference
        // to mark SkinnedMesh if node has skin.
        if (nodeDef.skin !== undefined) {
          meshDefs[nodeDef.mesh].isSkinnedMesh = true;
        }
      }

      if (nodeDef.camera !== undefined) {
        this._addNodeRef(this.cameraCache, nodeDef.camera);
      }
    }
  };

  /**
   * Counts references to shared node / Object3D resources. These resources
   * can be reused, or "instantiated", at multiple nodes in the scene
   * hierarchy. Mesh, Camera, and Light instances are instantiated and must
   * be marked. Non-scenegraph resources (like Materials, Geometries, and
   * Textures) can be reused directly and are not marked here.
   *
   * Example: CesiumMilkTruck sample model reuses "Wheel" meshes.
   */
  GLTFParser.prototype._addNodeRef = function(cache, index) {
    if (index === undefined) return;

    if (cache.refs[index] === undefined) {
      cache.refs[index] = cache.uses[index] = 0;
    }

    cache.refs[index]++;
  };

  /** Returns a reference to a shared resource, cloning it if necessary. */
  GLTFParser.prototype._getNodeRef = function(cache, index, object) {
    if (cache.refs[index] <= 1) return object;

    var ref = object.clone();

    ref.name += "_instance_" + cache.uses[index]++;

    return ref;
  };

  GLTFParser.prototype._invokeOne = function(func) {
    var extensions = Object.values(this.plugins);
    extensions.push(this);

    for (var i = 0; i < extensions.length; i++) {
      var result = func(extensions[i]);

      if (result) return result;
    }
  };

  GLTFParser.prototype._invokeAll = function(func) {
    var extensions = Object.values(this.plugins);
    extensions.unshift(this);

    var pending = [];

    for (var i = 0; i < extensions.length; i++) {
      var result = func(extensions[i]);

      if (result) pending.push(result);
    }

    return pending;
  };

  /**
   * Requests the specified dependency asynchronously, with caching.
   * @param {string} type
   * @param {number} index
   * @return {Promise<THREE.Object3D|THREE.Material|THREE.Texture|THREE.AnimationClip|ArrayBuffer|Object>}
   */
  GLTFParser.prototype.getDependency = function(type, index) {
    var cacheKey = type + ":" + index;
    var dependency = this.cache.get(cacheKey);

    if (!dependency) {
      switch (type) {
        case "scene":
          dependency = this.loadScene(index);
          break;

        case "node":
          dependency = this.loadNode(index);
          break;

        case "mesh":
          dependency = this._invokeOne(function(ext) {
            return ext.loadMesh && ext.loadMesh(index);
          });
          break;

        case "accessor":
          dependency = this.loadAccessor(index);
          break;

        case "bufferView":
          dependency = this._invokeOne(function(ext) {
            return ext.loadBufferView && ext.loadBufferView(index);
          });
          break;

        case "buffer":
          dependency = this.loadBuffer(index);
          break;

        case "material":
          dependency = this._invokeOne(function(ext) {
            return ext.loadMaterial && ext.loadMaterial(index);
          });
          break;

        case "texture":
          dependency = this._invokeOne(function(ext) {
            return ext.loadTexture && ext.loadTexture(index);
          });
          break;

        case "skin":
          dependency = this.loadSkin(index);
          break;

        case "animation":
          dependency = this.loadAnimation(index);
          break;

        case "camera":
          dependency = this.loadCamera(index);
          break;

        default:
          throw new Error("Unknown type: " + type);
      }

      this.cache.add(cacheKey, dependency);
    }

    return dependency;
  };

  /**
   * Requests all dependencies of the specified type asynchronously, with caching.
   * @param {string} type
   * @return {Promise<Array<Object>>}
   */
  GLTFParser.prototype.getDependencies = function(type) {
    var dependencies = this.cache.get(type);

    if (!dependencies) {
      var parser = this;
      var defs = this.json[type + (type === "mesh" ? "es" : "s")] || [];

      dependencies = Promise.all(
        defs.map(function(def, index) {
          return parser.getDependency(type, index);
        })
      );

      this.cache.add(type, dependencies);
    }

    return dependencies;
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
   * @param {number} bufferIndex
   * @return {Promise<ArrayBuffer>}
   */
  GLTFParser.prototype.loadBuffer = function(bufferIndex) {
    var bufferDef = this.json.buffers[bufferIndex];
    var loader = this.fileLoader;

    if (bufferDef.type && bufferDef.type !== "arraybuffer") {
      throw new Error(
        "THREE.GLTFLoader: " + bufferDef.type + " buffer type is not supported."
      );
    }

    // If present, GLB container is required to be the first buffer.
    if (bufferDef.uri === undefined && bufferIndex === 0) {
      return Promise.resolve(this.extensions[EXTENSIONS.KHR_BINARY_GLTF].body);
    }

    var options = this.options;

    return new Promise(function(resolve, reject) {
      loader.load(
        resolveURL(bufferDef.uri, options.path),
        resolve,
        undefined,
        function() {
          reject(
            new Error(
              'THREE.GLTFLoader: Failed to load buffer "' + bufferDef.uri + '".'
            )
          );
        }
      );
    });
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#buffers-and-buffer-views
   * @param {number} bufferViewIndex
   * @return {Promise<ArrayBuffer>}
   */
  GLTFParser.prototype.loadBufferView = function(bufferViewIndex) {
    var bufferViewDef = this.json.bufferViews[bufferViewIndex];

    return this.getDependency("buffer", bufferViewDef.buffer).then(function(
      buffer
    ) {
      var byteLength = bufferViewDef.byteLength || 0;
      var byteOffset = bufferViewDef.byteOffset || 0;
      return buffer.slice(byteOffset, byteOffset + byteLength);
    });
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#accessors
   * @param {number} accessorIndex
   * @return {Promise<THREE.BufferAttribute|THREE.InterleavedBufferAttribute>}
   */
  GLTFParser.prototype.loadAccessor = function(accessorIndex) {
    var parser = this;
    var json = this.json;

    var accessorDef = this.json.accessors[accessorIndex];

    if (
      accessorDef.bufferView === undefined &&
      accessorDef.sparse === undefined
    ) {
      // Ignore empty accessors, which may be used to declare runtime
      // information about attributes coming from another source (e.g. Draco
      // compression extension).
      return Promise.resolve(null);
    }

    var pendingBufferViews = [];

    if (accessorDef.bufferView !== undefined) {
      pendingBufferViews.push(
        this.getDependency("bufferView", accessorDef.bufferView)
      );
    } else {
      pendingBufferViews.push(null);
    }

    if (accessorDef.sparse !== undefined) {
      pendingBufferViews.push(
        this.getDependency("bufferView", accessorDef.sparse.indices.bufferView)
      );
      pendingBufferViews.push(
        this.getDependency("bufferView", accessorDef.sparse.values.bufferView)
      );
    }

    return Promise.all(pendingBufferViews).then(function(bufferViews) {
      var bufferView = bufferViews[0];

      var itemSize = WEBGL_TYPE_SIZES[accessorDef.type];
      var TypedArray = WEBGL_COMPONENT_TYPES[accessorDef.componentType];

      // For VEC3: itemSize is 3, elementBytes is 4, itemBytes is 12.
      var elementBytes = TypedArray.BYTES_PER_ELEMENT;
      var itemBytes = elementBytes * itemSize;
      var byteOffset = accessorDef.byteOffset || 0;
      var byteStride =
        accessorDef.bufferView !== undefined
          ? json.bufferViews[accessorDef.bufferView].byteStride
          : undefined;
      var normalized = accessorDef.normalized === true;
      var array, bufferAttribute;

      // The buffer is not interleaved if the stride is the item size in bytes.
      if (byteStride && byteStride !== itemBytes) {
        // Each "slice" of the buffer, as defined by 'count' elements of 'byteStride' bytes, gets its own InterleavedBuffer
        // This makes sure that IBA.count reflects accessor.count properly
        var ibSlice = Math.floor(byteOffset / byteStride);
        var ibCacheKey =
          "InterleavedBuffer:" +
          accessorDef.bufferView +
          ":" +
          accessorDef.componentType +
          ":" +
          ibSlice +
          ":" +
          accessorDef.count;
        var ib = parser.cache.get(ibCacheKey);

        if (!ib) {
          array = new TypedArray(
            bufferView,
            ibSlice * byteStride,
            (accessorDef.count * byteStride) / elementBytes
          );

          // Integer parameters to IB/IBA are in array elements, not bytes.
          ib = new THREE.InterleavedBuffer(array, byteStride / elementBytes);

          parser.cache.add(ibCacheKey, ib);
        }

        bufferAttribute = new THREE.InterleavedBufferAttribute(
          ib,
          itemSize,
          (byteOffset % byteStride) / elementBytes,
          normalized
        );
      } else {
        if (bufferView === null) {
          array = new TypedArray(accessorDef.count * itemSize);
        } else {
          array = new TypedArray(
            bufferView,
            byteOffset,
            accessorDef.count * itemSize
          );
        }

        bufferAttribute = new THREE.BufferAttribute(
          array,
          itemSize,
          normalized
        );
      }

      // https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#sparse-accessors
      if (accessorDef.sparse !== undefined) {
        var itemSizeIndices = WEBGL_TYPE_SIZES.SCALAR;
        var TypedArrayIndices =
          WEBGL_COMPONENT_TYPES[accessorDef.sparse.indices.componentType];

        var byteOffsetIndices = accessorDef.sparse.indices.byteOffset || 0;
        var byteOffsetValues = accessorDef.sparse.values.byteOffset || 0;

        var sparseIndices = new TypedArrayIndices(
          bufferViews[1],
          byteOffsetIndices,
          accessorDef.sparse.count * itemSizeIndices
        );
        var sparseValues = new TypedArray(
          bufferViews[2],
          byteOffsetValues,
          accessorDef.sparse.count * itemSize
        );

        if (bufferView !== null) {
          // Avoid modifying the original ArrayBuffer, if the bufferView wasn't initialized with zeroes.
          bufferAttribute = new THREE.BufferAttribute(
            bufferAttribute.array.slice(),
            bufferAttribute.itemSize,
            bufferAttribute.normalized
          );
        }

        for (var i = 0, il = sparseIndices.length; i < il; i++) {
          var index = sparseIndices[i];

          bufferAttribute.setX(index, sparseValues[i * itemSize]);
          if (itemSize >= 2)
            bufferAttribute.setY(index, sparseValues[i * itemSize + 1]);
          if (itemSize >= 3)
            bufferAttribute.setZ(index, sparseValues[i * itemSize + 2]);
          if (itemSize >= 4)
            bufferAttribute.setW(index, sparseValues[i * itemSize + 3]);
          if (itemSize >= 5)
            throw new Error(
              "THREE.GLTFLoader: Unsupported itemSize in sparse BufferAttribute."
            );
        }
      }

      return bufferAttribute;
    });
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#textures
   * @param {number} textureIndex
   * @return {Promise<THREE.Texture>}
   */
  GLTFParser.prototype.loadTexture = function(textureIndex) {
    var parser = this;
    var json = this.json;
    var options = this.options;

    var textureDef = json.textures[textureIndex];

    var textureExtensions = textureDef.extensions || {};

    var source;

    if (textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]) {
      source =
        json.images[textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS].source];
    } else {
      source = json.images[textureDef.source];
    }

    var loader;

    if (source.uri) {
      loader = options.manager.getHandler(source.uri);
    }

    if (!loader) {
      loader = textureExtensions[EXTENSIONS.MSFT_TEXTURE_DDS]
        ? parser.extensions[EXTENSIONS.MSFT_TEXTURE_DDS].ddsLoader
        : this.textureLoader;
    }

    return this.loadTextureImage(textureIndex, source, loader);
  };

  GLTFParser.prototype.loadTextureImage = function(
    textureIndex,
    source,
    loader
  ) {
    var parser = this;
    var json = this.json;
    var options = this.options;

    var textureDef = json.textures[textureIndex];

    var URL = self.URL || self.webkitURL;

    var sourceURI = source.uri;
    var isObjectURL = false;
    var hasAlpha = true;

    if (source.mimeType === "image/jpeg") hasAlpha = false;

    if (source.bufferView !== undefined) {
      // Load binary image data from bufferView, if provided.

      sourceURI = parser
        .getDependency("bufferView", source.bufferView)
        .then(function(bufferView) {
          if (source.mimeType === "image/png") {
            // Inspect the PNG 'IHDR' chunk to determine whether the image could have an
            // alpha channel. This check is conservative — the image could have an alpha
            // channel with all values == 1, and the indexed type (colorType == 3) only
            // sometimes contains alpha.
            //
            // https://en.wikipedia.org/wiki/Portable_Network_Graphics#File_header
            var colorType = new DataView(bufferView, 25, 1).getUint8(0, false);
            hasAlpha = colorType === 6 || colorType === 4 || colorType === 3;
          }

          isObjectURL = true;
          var blob = new Blob([bufferView], { type: source.mimeType });
          sourceURI = URL.createObjectURL(blob);
          return sourceURI;
        });
    }

    return Promise.resolve(sourceURI)
      .then(function(sourceURI) {
        return new Promise(function(resolve, reject) {
          var onLoad = resolve;

          if (loader.isImageBitmapLoader === true) {
            onLoad = function(imageBitmap) {
              resolve(new THREE.CanvasTexture(imageBitmap));
            };
          }

          loader.load(
            resolveURL(sourceURI, options.path),
            onLoad,
            undefined,
            reject
          );
        });
      })
      .then(function(texture) {
        // Clean up resources and configure Texture.

        if (isObjectURL === true) {
          URL.revokeObjectURL(sourceURI);
        }

        texture.flipY = false;

        if (textureDef.name) texture.name = textureDef.name;

        // When there is definitely no alpha channel in the texture, set RGBFormat to save space.
        if (!hasAlpha) texture.format = THREE.RGBFormat;

        var samplers = json.samplers || {};
        var sampler = samplers[textureDef.sampler] || {};

        texture.magFilter =
          WEBGL_FILTERS[sampler.magFilter] || THREE.LinearFilter;
        texture.minFilter =
          WEBGL_FILTERS[sampler.minFilter] || THREE.LinearMipmapLinearFilter;
        texture.wrapS = WEBGL_WRAPPINGS[sampler.wrapS] || THREE.RepeatWrapping;
        texture.wrapT = WEBGL_WRAPPINGS[sampler.wrapT] || THREE.RepeatWrapping;

        parser.associations.set(texture, {
          type: "textures",
          index: textureIndex
        });

        return texture;
      });
  };

  /**
   * Asynchronously assigns a texture to the given material parameters.
   * @param {Object} materialParams
   * @param {string} mapName
   * @param {Object} mapDef
   * @return {Promise}
   */
  GLTFParser.prototype.assignTexture = function(
    materialParams,
    mapName,
    mapDef
  ) {
    var parser = this;

    return this.getDependency("texture", mapDef.index).then(function(texture) {
      // Materials sample aoMap from UV set 1 and other maps from UV set 0 - this can't be configured
      // However, we will copy UV set 0 to UV set 1 on demand for aoMap
      if (
        mapDef.texCoord !== undefined &&
        mapDef.texCoord != 0 &&
        !(mapName === "aoMap" && mapDef.texCoord == 1)
      ) {
        console.warn(
          "THREE.GLTFLoader: Custom UV set " +
            mapDef.texCoord +
            " for texture " +
            mapName +
            " not yet supported."
        );
      }

      if (parser.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]) {
        var transform =
          mapDef.extensions !== undefined
            ? mapDef.extensions[EXTENSIONS.KHR_TEXTURE_TRANSFORM]
            : undefined;

        if (transform) {
          var gltfReference = parser.associations.get(texture);
          texture = parser.extensions[
            EXTENSIONS.KHR_TEXTURE_TRANSFORM
          ].extendTexture(texture, transform);
          parser.associations.set(texture, gltfReference);
        }
      }

      materialParams[mapName] = texture;
    });
  };

  /**
   * Assigns final material to a Mesh, Line, or Points instance. The instance
   * already has a material (generated from the glTF material options alone)
   * but reuse of the same glTF material may require multiple threejs materials
   * to accomodate different primitive types, defines, etc. New materials will
   * be created if necessary, and reused from a cache.
   * @param  {THREE.Object3D} mesh Mesh, Line, or Points instance.
   */
  GLTFParser.prototype.assignFinalMaterial = function(mesh) {
    var geometry = mesh.geometry;
    var material = mesh.material;

    var useVertexTangents = geometry.attributes.tangent !== undefined;
    var useVertexColors = geometry.attributes.color !== undefined;
    var useFlatShading = geometry.attributes.normal === undefined;
    var useSkinning = mesh.isSkinnedMesh === true;
    var useMorphTargets = Object.keys(geometry.morphAttributes).length > 0;
    var useMorphNormals =
      useMorphTargets && geometry.morphAttributes.normal !== undefined;

    if (mesh.isPoints) {
      var cacheKey = "PointsMaterial:" + material.uuid;

      var pointsMaterial = this.cache.get(cacheKey);

      if (!pointsMaterial) {
        pointsMaterial = new THREE.PointsMaterial();
        THREE.Material.prototype.copy.call(pointsMaterial, material);
        pointsMaterial.color.copy(material.color);
        pointsMaterial.map = material.map;
        pointsMaterial.sizeAttenuation = false; // glTF spec says points should be 1px

        this.cache.add(cacheKey, pointsMaterial);
      }

      material = pointsMaterial;
    } else if (mesh.isLine) {
      var cacheKey = "LineBasicMaterial:" + material.uuid;

      var lineMaterial = this.cache.get(cacheKey);

      if (!lineMaterial) {
        lineMaterial = new THREE.LineBasicMaterial();
        THREE.Material.prototype.copy.call(lineMaterial, material);
        lineMaterial.color.copy(material.color);

        this.cache.add(cacheKey, lineMaterial);
      }

      material = lineMaterial;
    }

    // Clone the material if it will be modified
    if (
      useVertexTangents ||
      useVertexColors ||
      useFlatShading ||
      useSkinning ||
      useMorphTargets
    ) {
      var cacheKey = "ClonedMaterial:" + material.uuid + ":";

      if (material.isGLTFSpecularGlossinessMaterial)
        cacheKey += "specular-glossiness:";
      if (useSkinning) cacheKey += "skinning:";
      if (useVertexTangents) cacheKey += "vertex-tangents:";
      if (useVertexColors) cacheKey += "vertex-colors:";
      if (useFlatShading) cacheKey += "flat-shading:";
      if (useMorphTargets) cacheKey += "morph-targets:";
      if (useMorphNormals) cacheKey += "morph-normals:";

      var cachedMaterial = this.cache.get(cacheKey);

      if (!cachedMaterial) {
        cachedMaterial = material.clone();

        if (useSkinning) cachedMaterial.skinning = true;
        if (useVertexColors) cachedMaterial.vertexColors = true;
        if (useFlatShading) cachedMaterial.flatShading = true;
        if (useMorphTargets) cachedMaterial.morphTargets = true;
        if (useMorphNormals) cachedMaterial.morphNormals = true;

        if (useVertexTangents) {
          cachedMaterial.vertexTangents = true;

          // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
          if (cachedMaterial.normalScale) cachedMaterial.normalScale.y *= -1;
          if (cachedMaterial.clearcoatNormalScale)
            cachedMaterial.clearcoatNormalScale.y *= -1;
        }

        this.cache.add(cacheKey, cachedMaterial);

        this.associations.set(cachedMaterial, this.associations.get(material));
      }

      material = cachedMaterial;
    }

    // workarounds for mesh and geometry

    if (
      material.aoMap &&
      geometry.attributes.uv2 === undefined &&
      geometry.attributes.uv !== undefined
    ) {
      geometry.setAttribute("uv2", geometry.attributes.uv);
    }

    mesh.material = material;
  };

  GLTFParser.prototype.getMaterialType = function(/* materialIndex */) {
    return THREE.MeshStandardMaterial;
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#materials
   * @param {number} materialIndex
   * @return {Promise<THREE.Material>}
   */
  GLTFParser.prototype.loadMaterial = function(materialIndex) {
    var parser = this;
    var json = this.json;
    var extensions = this.extensions;
    var materialDef = json.materials[materialIndex];

    var materialType;
    var materialParams = {};
    var materialExtensions = materialDef.extensions || {};

    var pending = [];

    if (materialExtensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS]) {
      var sgExtension =
        extensions[EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS];
      materialType = sgExtension.getMaterialType();
      pending.push(
        sgExtension.extendParams(materialParams, materialDef, parser)
      );
    } else if (materialExtensions[EXTENSIONS.KHR_MATERIALS_UNLIT]) {
      var kmuExtension = extensions[EXTENSIONS.KHR_MATERIALS_UNLIT];
      materialType = kmuExtension.getMaterialType();
      pending.push(
        kmuExtension.extendParams(materialParams, materialDef, parser)
      );
    } else {
      // Specification:
      // https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#metallic-roughness-material

      var metallicRoughness = materialDef.pbrMetallicRoughness || {};

      materialParams.color = new THREE.Color(1.0, 1.0, 1.0);
      materialParams.opacity = 1.0;

      if (Array.isArray(metallicRoughness.baseColorFactor)) {
        var array = metallicRoughness.baseColorFactor;

        materialParams.color.fromArray(array);
        materialParams.opacity = array[3];
      }

      if (metallicRoughness.baseColorTexture !== undefined) {
        pending.push(
          parser.assignTexture(
            materialParams,
            "map",
            metallicRoughness.baseColorTexture
          )
        );
      }

      materialParams.metalness =
        metallicRoughness.metallicFactor !== undefined
          ? metallicRoughness.metallicFactor
          : 1.0;
      materialParams.roughness =
        metallicRoughness.roughnessFactor !== undefined
          ? metallicRoughness.roughnessFactor
          : 1.0;

      if (metallicRoughness.metallicRoughnessTexture !== undefined) {
        pending.push(
          parser.assignTexture(
            materialParams,
            "metalnessMap",
            metallicRoughness.metallicRoughnessTexture
          )
        );
        pending.push(
          parser.assignTexture(
            materialParams,
            "roughnessMap",
            metallicRoughness.metallicRoughnessTexture
          )
        );
      }

      materialType = this._invokeOne(function(ext) {
        return ext.getMaterialType && ext.getMaterialType(materialIndex);
      });

      pending.push(
        Promise.all(
          this._invokeAll(function(ext) {
            return (
              ext.extendMaterialParams &&
              ext.extendMaterialParams(materialIndex, materialParams)
            );
          })
        )
      );
    }

    if (materialDef.doubleSided === true) {
      materialParams.side = THREE.DoubleSide;
    }

    var alphaMode = materialDef.alphaMode || ALPHA_MODES.OPAQUE;

    if (alphaMode === ALPHA_MODES.BLEND) {
      materialParams.transparent = true;

      // See: https://github.com/mrdoob/three.js/issues/17706
      materialParams.depthWrite = false;
    } else {
      materialParams.transparent = false;

      if (alphaMode === ALPHA_MODES.MASK) {
        materialParams.alphaTest =
          materialDef.alphaCutoff !== undefined ? materialDef.alphaCutoff : 0.5;
      }
    }

    if (
      materialDef.normalTexture !== undefined &&
      materialType !== THREE.MeshBasicMaterial
    ) {
      pending.push(
        parser.assignTexture(
          materialParams,
          "normalMap",
          materialDef.normalTexture
        )
      );

      // https://github.com/mrdoob/three.js/issues/11438#issuecomment-507003995
      materialParams.normalScale = new THREE.Vector2(1, -1);

      if (materialDef.normalTexture.scale !== undefined) {
        materialParams.normalScale.set(
          materialDef.normalTexture.scale,
          -materialDef.normalTexture.scale
        );
      }
    }

    if (
      materialDef.occlusionTexture !== undefined &&
      materialType !== THREE.MeshBasicMaterial
    ) {
      pending.push(
        parser.assignTexture(
          materialParams,
          "aoMap",
          materialDef.occlusionTexture
        )
      );

      if (materialDef.occlusionTexture.strength !== undefined) {
        materialParams.aoMapIntensity = materialDef.occlusionTexture.strength;
      }
    }

    if (
      materialDef.emissiveFactor !== undefined &&
      materialType !== THREE.MeshBasicMaterial
    ) {
      materialParams.emissive = new THREE.Color().fromArray(
        materialDef.emissiveFactor
      );
    }

    if (
      materialDef.emissiveTexture !== undefined &&
      materialType !== THREE.MeshBasicMaterial
    ) {
      pending.push(
        parser.assignTexture(
          materialParams,
          "emissiveMap",
          materialDef.emissiveTexture
        )
      );
    }

    return Promise.all(pending).then(function() {
      var material;

      if (materialType === GLTFMeshStandardSGMaterial) {
        material = extensions[
          EXTENSIONS.KHR_MATERIALS_PBR_SPECULAR_GLOSSINESS
        ].createMaterial(materialParams);
      } else {
        material = new materialType(materialParams);
      }

      if (materialDef.name) material.name = materialDef.name;

      // baseColorTexture, emissiveTexture, and specularGlossinessTexture use sRGB encoding.
      if (material.map) material.map.encoding = THREE.sRGBEncoding;
      if (material.emissiveMap)
        material.emissiveMap.encoding = THREE.sRGBEncoding;

      assignExtrasToUserData(material, materialDef);

      parser.associations.set(material, {
        type: "materials",
        index: materialIndex
      });

      if (materialDef.extensions)
        addUnknownExtensionsToUserData(extensions, material, materialDef);

      return material;
    });
  };

  /** When Object3D instances are targeted by animation, they need unique names. */
  GLTFParser.prototype.createUniqueName = function(originalName) {
    var sanitizedName = THREE.PropertyBinding.sanitizeNodeName(
      originalName || ""
    );

    var name = sanitizedName;

    for (var i = 1; this.nodeNamesUsed[name]; ++i) {
      name = sanitizedName + "_" + i;
    }

    this.nodeNamesUsed[name] = true;

    return name;
  };

  /**
   * @param {THREE.BufferGeometry} geometry
   * @param {GLTF.Primitive} primitiveDef
   * @param {GLTFParser} parser
   */
  function computeBounds(geometry, primitiveDef, parser) {
    var attributes = primitiveDef.attributes;

    var box = new THREE.Box3();

    if (attributes.POSITION !== undefined) {
      var accessor = parser.json.accessors[attributes.POSITION];

      var min = accessor.min;
      var max = accessor.max;

      // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

      if (min !== undefined && max !== undefined) {
        box.set(
          new THREE.Vector3(min[0], min[1], min[2]),
          new THREE.Vector3(max[0], max[1], max[2])
        );
      } else {
        console.warn(
          "THREE.GLTFLoader: Missing min/max properties for accessor POSITION."
        );

        return;
      }
    } else {
      return;
    }

    var targets = primitiveDef.targets;

    if (targets !== undefined) {
      var maxDisplacement = new THREE.Vector3();
      var vector = new THREE.Vector3();

      for (var i = 0, il = targets.length; i < il; i++) {
        var target = targets[i];

        if (target.POSITION !== undefined) {
          var accessor = parser.json.accessors[target.POSITION];
          var min = accessor.min;
          var max = accessor.max;

          // glTF requires 'min' and 'max', but VRM (which extends glTF) currently ignores that requirement.

          if (min !== undefined && max !== undefined) {
            // we need to get max of absolute components because target weight is [-1,1]
            vector.setX(Math.max(Math.abs(min[0]), Math.abs(max[0])));
            vector.setY(Math.max(Math.abs(min[1]), Math.abs(max[1])));
            vector.setZ(Math.max(Math.abs(min[2]), Math.abs(max[2])));

            // Note: this assumes that the sum of all weights is at most 1. This isn't quite correct - it's more conservative
            // to assume that each target can have a max weight of 1. However, for some use cases - notably, when morph targets
            // are used to implement key-frame animations and as such only two are active at a time - this results in very large
            // boxes. So for now we make a box that's sometimes a touch too small but is hopefully mostly of reasonable size.
            maxDisplacement.max(vector);
          } else {
            console.warn(
              "THREE.GLTFLoader: Missing min/max properties for accessor POSITION."
            );
          }
        }
      }

      // As per comment above this box isn't conservative, but has a reasonable size for a very large number of morph targets.
      box.expandByVector(maxDisplacement);
    }

    geometry.boundingBox = box;

    var sphere = new THREE.Sphere();

    box.getCenter(sphere.center);
    sphere.radius = box.min.distanceTo(box.max) / 2;

    geometry.boundingSphere = sphere;
  }

  /**
   * @param {THREE.BufferGeometry} geometry
   * @param {GLTF.Primitive} primitiveDef
   * @param {GLTFParser} parser
   * @return {Promise<THREE.BufferGeometry>}
   */
  function addPrimitiveAttributes(geometry, primitiveDef, parser) {
    var attributes = primitiveDef.attributes;

    var pending = [];

    function assignAttributeAccessor(accessorIndex, attributeName) {
      return parser
        .getDependency("accessor", accessorIndex)
        .then(function(accessor) {
          geometry.setAttribute(attributeName, accessor);
        });
    }

    for (var gltfAttributeName in attributes) {
      var threeAttributeName =
        ATTRIBUTES[gltfAttributeName] || gltfAttributeName.toLowerCase();

      // Skip attributes already provided by e.g. Draco extension.
      if (threeAttributeName in geometry.attributes) continue;

      pending.push(
        assignAttributeAccessor(
          attributes[gltfAttributeName],
          threeAttributeName
        )
      );
    }

    if (primitiveDef.indices !== undefined && !geometry.index) {
      var accessor = parser
        .getDependency("accessor", primitiveDef.indices)
        .then(function(accessor) {
          geometry.setIndex(accessor);
        });

      pending.push(accessor);
    }

    assignExtrasToUserData(geometry, primitiveDef);

    computeBounds(geometry, primitiveDef, parser);

    return Promise.all(pending).then(function() {
      return primitiveDef.targets !== undefined
        ? addMorphTargets(geometry, primitiveDef.targets, parser)
        : geometry;
    });
  }

  /**
   * @param {THREE.BufferGeometry} geometry
   * @param {Number} drawMode
   * @return {THREE.BufferGeometry}
   */
  function toTrianglesDrawMode(geometry, drawMode) {
    var index = geometry.getIndex();

    // generate index if not present

    if (index === null) {
      var indices = [];

      var position = geometry.getAttribute("position");

      if (position !== undefined) {
        for (var i = 0; i < position.count; i++) {
          indices.push(i);
        }

        geometry.setIndex(indices);
        index = geometry.getIndex();
      } else {
        console.error(
          "THREE.GLTFLoader.toTrianglesDrawMode(): Undefined position attribute. Processing not possible."
        );
        return geometry;
      }
    }

    //

    var numberOfTriangles = index.count - 2;
    var newIndices = [];

    if (drawMode === THREE.TriangleFanDrawMode) {
      // gl.TRIANGLE_FAN

      for (var i = 1; i <= numberOfTriangles; i++) {
        newIndices.push(index.getX(0));
        newIndices.push(index.getX(i));
        newIndices.push(index.getX(i + 1));
      }
    } else {
      // gl.TRIANGLE_STRIP

      for (var i = 0; i < numberOfTriangles; i++) {
        if (i % 2 === 0) {
          newIndices.push(index.getX(i));
          newIndices.push(index.getX(i + 1));
          newIndices.push(index.getX(i + 2));
        } else {
          newIndices.push(index.getX(i + 2));
          newIndices.push(index.getX(i + 1));
          newIndices.push(index.getX(i));
        }
      }
    }

    if (newIndices.length / 3 !== numberOfTriangles) {
      console.error(
        "THREE.GLTFLoader.toTrianglesDrawMode(): Unable to generate correct amount of triangles."
      );
    }

    // build final geometry

    var newGeometry = geometry.clone();
    newGeometry.setIndex(newIndices);

    return newGeometry;
  }

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#geometry
   *
   * Creates BufferGeometries from primitives.
   *
   * @param {Array<GLTF.Primitive>} primitives
   * @return {Promise<Array<THREE.BufferGeometry>>}
   */
  GLTFParser.prototype.loadGeometries = function(primitives) {
    var parser = this;
    var extensions = this.extensions;
    var cache = this.primitiveCache;

    function createDracoPrimitive(primitive) {
      return extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
        .decodePrimitive(primitive, parser)
        .then(function(geometry) {
          return addPrimitiveAttributes(geometry, primitive, parser);
        });
    }

    var pending = [];

    for (var i = 0, il = primitives.length; i < il; i++) {
      var primitive = primitives[i];
      var cacheKey = createPrimitiveKey(primitive);

      // See if we've already created this geometry
      var cached = cache[cacheKey];

      if (cached) {
        // Use the cached geometry if it exists
        pending.push(cached.promise);
      } else {
        var geometryPromise;

        if (
          primitive.extensions &&
          primitive.extensions[EXTENSIONS.KHR_DRACO_MESH_COMPRESSION]
        ) {
          // Use DRACO geometry if available
          geometryPromise = createDracoPrimitive(primitive);
        } else {
          // Otherwise create a new geometry
          geometryPromise = addPrimitiveAttributes(
            new THREE.BufferGeometry(),
            primitive,
            parser
          );
        }

        // Cache this geometry
        cache[cacheKey] = { primitive: primitive, promise: geometryPromise };

        pending.push(geometryPromise);
      }
    }

    return Promise.all(pending);
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#meshes
   * @param {number} meshIndex
   * @return {Promise<THREE.Group|THREE.Mesh|THREE.SkinnedMesh>}
   */
  GLTFParser.prototype.loadMesh = function(meshIndex) {
    var parser = this;
    var json = this.json;
    var extensions = this.extensions;

    var meshDef = json.meshes[meshIndex];
    var primitives = meshDef.primitives;

    var pending = [];

    for (var i = 0, il = primitives.length; i < il; i++) {
      var material =
        primitives[i].material === undefined
          ? createDefaultMaterial(this.cache)
          : this.getDependency("material", primitives[i].material);

      pending.push(material);
    }

    pending.push(parser.loadGeometries(primitives));

    return Promise.all(pending).then(function(results) {
      var materials = results.slice(0, results.length - 1);
      var geometries = results[results.length - 1];

      var meshes = [];

      for (var i = 0, il = geometries.length; i < il; i++) {
        var geometry = geometries[i];
        var primitive = primitives[i];

        // 1. create Mesh

        var mesh;

        var material = materials[i];

        if (
          primitive.mode === WEBGL_CONSTANTS.TRIANGLES ||
          primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP ||
          primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN ||
          primitive.mode === undefined
        ) {
          // .isSkinnedMesh isn't in glTF spec. See ._markDefs()
          mesh =
            meshDef.isSkinnedMesh === true
              ? new THREE.SkinnedMesh(geometry, material)
              : new THREE.Mesh(geometry, material);

          // Fix double sided rendered models on certain mobile devices, see https://github.com/mrdoob/three.js/issues/20997#issuecomment-756082184

          if (
            material.isMeshStandardMaterial === true &&
            material.side === THREE.DoubleSide &&
            geometry.getIndex() !== null &&
            geometry.hasAttribute("position") === true &&
            geometry.hasAttribute("normal") === true &&
            geometry.hasAttribute("uv") === true &&
            geometry.hasAttribute("tangent") === false
          ) {
            geometry.computeTangents();
            material.vertexTangents = true;
          }

          if (
            mesh.isSkinnedMesh === true &&
            !mesh.geometry.attributes.skinWeight.normalized
          ) {
            // we normalize floating point skin weight array to fix malformed assets (see #15319)
            // it's important to skip this for non-float32 data since normalizeSkinWeights assumes non-normalized inputs
            mesh.normalizeSkinWeights();
          }

          if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_STRIP) {
            mesh.geometry = toTrianglesDrawMode(
              mesh.geometry,
              THREE.TriangleStripDrawMode
            );
          } else if (primitive.mode === WEBGL_CONSTANTS.TRIANGLE_FAN) {
            mesh.geometry = toTrianglesDrawMode(
              mesh.geometry,
              THREE.TriangleFanDrawMode
            );
          }
        } else if (primitive.mode === WEBGL_CONSTANTS.LINES) {
          mesh = new THREE.LineSegments(geometry, material);
        } else if (primitive.mode === WEBGL_CONSTANTS.LINE_STRIP) {
          mesh = new THREE.Line(geometry, material);
        } else if (primitive.mode === WEBGL_CONSTANTS.LINE_LOOP) {
          mesh = new THREE.LineLoop(geometry, material);
        } else if (primitive.mode === WEBGL_CONSTANTS.POINTS) {
          mesh = new THREE.Points(geometry, material);
        } else {
          throw new Error(
            "THREE.GLTFLoader: Primitive mode unsupported: " + primitive.mode
          );
        }

        if (Object.keys(mesh.geometry.morphAttributes).length > 0) {
          updateMorphTargets(mesh, meshDef);
        }

        mesh.name = parser.createUniqueName(
          meshDef.name || "mesh_" + meshIndex
        );

        assignExtrasToUserData(mesh, meshDef);

        if (primitive.extensions)
          addUnknownExtensionsToUserData(extensions, mesh, primitive);

        parser.assignFinalMaterial(mesh);

        meshes.push(mesh);
      }

      if (meshes.length === 1) {
        return meshes[0];
      }

      var group = new THREE.Group();

      for (var i = 0, il = meshes.length; i < il; i++) {
        group.add(meshes[i]);
      }

      return group;
    });
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#cameras
   * @param {number} cameraIndex
   * @return {Promise<THREE.Camera>}
   */
  GLTFParser.prototype.loadCamera = function(cameraIndex) {
    var camera;
    var cameraDef = this.json.cameras[cameraIndex];
    var params = cameraDef[cameraDef.type];

    if (!params) {
      console.warn("THREE.GLTFLoader: Missing camera parameters.");
      return;
    }

    if (cameraDef.type === "perspective") {
      camera = new THREE.PerspectiveCamera(
        THREE.MathUtils.radToDeg(params.yfov),
        params.aspectRatio || 1,
        params.znear || 1,
        params.zfar || 2e6
      );
    } else if (cameraDef.type === "orthographic") {
      camera = new THREE.OrthographicCamera(
        -params.xmag,
        params.xmag,
        params.ymag,
        -params.ymag,
        params.znear,
        params.zfar
      );
    }

    if (cameraDef.name) camera.name = this.createUniqueName(cameraDef.name);

    assignExtrasToUserData(camera, cameraDef);

    return Promise.resolve(camera);
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#skins
   * @param {number} skinIndex
   * @return {Promise<Object>}
   */
  GLTFParser.prototype.loadSkin = function(skinIndex) {
    var skinDef = this.json.skins[skinIndex];

    var skinEntry = { joints: skinDef.joints };

    if (skinDef.inverseBindMatrices === undefined) {
      return Promise.resolve(skinEntry);
    }

    return this.getDependency("accessor", skinDef.inverseBindMatrices).then(
      function(accessor) {
        skinEntry.inverseBindMatrices = accessor;

        return skinEntry;
      }
    );
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#animations
   * @param {number} animationIndex
   * @return {Promise<THREE.AnimationClip>}
   */
  GLTFParser.prototype.loadAnimation = function(animationIndex) {
    var json = this.json;

    var animationDef = json.animations[animationIndex];

    var pendingNodes = [];
    var pendingInputAccessors = [];
    var pendingOutputAccessors = [];
    var pendingSamplers = [];
    var pendingTargets = [];

    for (var i = 0, il = animationDef.channels.length; i < il; i++) {
      var channel = animationDef.channels[i];
      var sampler = animationDef.samplers[channel.sampler];
      var target = channel.target;
      var name = target.node !== undefined ? target.node : target.id; // NOTE: target.id is deprecated.
      var input =
        animationDef.parameters !== undefined
          ? animationDef.parameters[sampler.input]
          : sampler.input;
      var output =
        animationDef.parameters !== undefined
          ? animationDef.parameters[sampler.output]
          : sampler.output;

      pendingNodes.push(this.getDependency("node", name));
      pendingInputAccessors.push(this.getDependency("accessor", input));
      pendingOutputAccessors.push(this.getDependency("accessor", output));
      pendingSamplers.push(sampler);
      pendingTargets.push(target);
    }

    return Promise.all([
      Promise.all(pendingNodes),
      Promise.all(pendingInputAccessors),
      Promise.all(pendingOutputAccessors),
      Promise.all(pendingSamplers),
      Promise.all(pendingTargets)
    ]).then(function(dependencies) {
      var nodes = dependencies[0];
      var inputAccessors = dependencies[1];
      var outputAccessors = dependencies[2];
      var samplers = dependencies[3];
      var targets = dependencies[4];

      var tracks = [];

      for (var i = 0, il = nodes.length; i < il; i++) {
        var node = nodes[i];
        var inputAccessor = inputAccessors[i];
        var outputAccessor = outputAccessors[i];
        var sampler = samplers[i];
        var target = targets[i];

        if (node === undefined) continue;

        node.updateMatrix();
        node.matrixAutoUpdate = true;

        var TypedKeyframeTrack;

        switch (PATH_PROPERTIES[target.path]) {
          case PATH_PROPERTIES.weights:
            TypedKeyframeTrack = THREE.NumberKeyframeTrack;
            break;

          case PATH_PROPERTIES.rotation:
            TypedKeyframeTrack = THREE.QuaternionKeyframeTrack;
            break;

          case PATH_PROPERTIES.position:
          case PATH_PROPERTIES.scale:
          default:
            TypedKeyframeTrack = THREE.VectorKeyframeTrack;
            break;
        }

        var targetName = node.name ? node.name : node.uuid;

        var interpolation =
          sampler.interpolation !== undefined
            ? INTERPOLATION[sampler.interpolation]
            : THREE.InterpolateLinear;

        var targetNames = [];

        if (PATH_PROPERTIES[target.path] === PATH_PROPERTIES.weights) {
          // Node may be a THREE.Group (glTF mesh with several primitives) or a THREE.Mesh.
          node.traverse(function(object) {
            if (object.isMesh === true && object.morphTargetInfluences) {
              targetNames.push(object.name ? object.name : object.uuid);
            }
          });
        } else {
          targetNames.push(targetName);
        }

        var outputArray = outputAccessor.array;

        if (outputAccessor.normalized) {
          var scale;

          if (outputArray.constructor === Int8Array) {
            scale = 1 / 127;
          } else if (outputArray.constructor === Uint8Array) {
            scale = 1 / 255;
          } else if (outputArray.constructor == Int16Array) {
            scale = 1 / 32767;
          } else if (outputArray.constructor === Uint16Array) {
            scale = 1 / 65535;
          } else {
            throw new Error(
              "THREE.GLTFLoader: Unsupported output accessor component type."
            );
          }

          var scaled = new Float32Array(outputArray.length);

          for (var j = 0, jl = outputArray.length; j < jl; j++) {
            scaled[j] = outputArray[j] * scale;
          }

          outputArray = scaled;
        }

        for (var j = 0, jl = targetNames.length; j < jl; j++) {
          var track = new TypedKeyframeTrack(
            targetNames[j] + "." + PATH_PROPERTIES[target.path],
            inputAccessor.array,
            outputArray,
            interpolation
          );

          // Override interpolation with custom factory method.
          if (sampler.interpolation === "CUBICSPLINE") {
            track.createInterpolant = function InterpolantFactoryMethodGLTFCubicSpline(
              result
            ) {
              // A CUBICSPLINE keyframe in glTF has three output values for each input value,
              // representing inTangent, splineVertex, and outTangent. As a result, track.getValueSize()
              // must be divided by three to get the interpolant's sampleSize argument.

              return new GLTFCubicSplineInterpolant(
                this.times,
                this.values,
                this.getValueSize() / 3,
                result
              );
            };

            // Mark as CUBICSPLINE. `track.getInterpolation()` doesn't support custom interpolants.
            track.createInterpolant.isInterpolantFactoryMethodGLTFCubicSpline = true;
          }

          tracks.push(track);
        }
      }

      var name = animationDef.name
        ? animationDef.name
        : "animation_" + animationIndex;

      return new THREE.AnimationClip(name, undefined, tracks);
    });
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#nodes-and-hierarchy
   * @param {number} nodeIndex
   * @return {Promise<THREE.Object3D>}
   */
  GLTFParser.prototype.loadNode = function(nodeIndex) {
    var json = this.json;
    var extensions = this.extensions;
    var parser = this;

    var nodeDef = json.nodes[nodeIndex];

    // reserve node's name before its dependencies, so the root has the intended name.
    var nodeName = nodeDef.name ? parser.createUniqueName(nodeDef.name) : "";

    return (function() {
      var pending = [];

      if (nodeDef.mesh !== undefined) {
        pending.push(
          parser.getDependency("mesh", nodeDef.mesh).then(function(mesh) {
            var node = parser._getNodeRef(parser.meshCache, nodeDef.mesh, mesh);

            // if weights are provided on the node, override weights on the mesh.
            if (nodeDef.weights !== undefined) {
              node.traverse(function(o) {
                if (!o.isMesh) return;

                for (var i = 0, il = nodeDef.weights.length; i < il; i++) {
                  o.morphTargetInfluences[i] = nodeDef.weights[i];
                }
              });
            }

            return node;
          })
        );
      }

      if (nodeDef.camera !== undefined) {
        pending.push(
          parser.getDependency("camera", nodeDef.camera).then(function(camera) {
            return parser._getNodeRef(
              parser.cameraCache,
              nodeDef.camera,
              camera
            );
          })
        );
      }

      parser
        ._invokeAll(function(ext) {
          return (
            ext.createNodeAttachment && ext.createNodeAttachment(nodeIndex)
          );
        })
        .forEach(function(promise) {
          pending.push(promise);
        });

      return Promise.all(pending);
    })().then(function(objects) {
      var node;

      // .isBone isn't in glTF spec. See ._markDefs
      if (nodeDef.isBone === true) {
        node = new THREE.Bone();
      } else if (objects.length > 1) {
        node = new THREE.Group();
      } else if (objects.length === 1) {
        node = objects[0];
      } else {
        node = new THREE.Object3D();
      }

      if (node !== objects[0]) {
        for (var i = 0, il = objects.length; i < il; i++) {
          node.add(objects[i]);
        }
      }

      if (nodeDef.name) {
        node.userData.name = nodeDef.name;
        node.name = nodeName;
      }

      assignExtrasToUserData(node, nodeDef);

      if (nodeDef.extensions)
        addUnknownExtensionsToUserData(extensions, node, nodeDef);

      if (nodeDef.matrix !== undefined) {
        var matrix = new THREE.Matrix4();
        matrix.fromArray(nodeDef.matrix);
        node.applyMatrix4(matrix);
      } else {
        if (nodeDef.translation !== undefined) {
          node.position.fromArray(nodeDef.translation);
        }

        if (nodeDef.rotation !== undefined) {
          node.quaternion.fromArray(nodeDef.rotation);
        }

        if (nodeDef.scale !== undefined) {
          node.scale.fromArray(nodeDef.scale);
        }
      }

      parser.associations.set(node, { type: "nodes", index: nodeIndex });

      return node;
    });
  };

  /**
   * Specification: https://github.com/KhronosGroup/glTF/tree/master/specification/2.0#scenes
   * @param {number} sceneIndex
   * @return {Promise<THREE.Group>}
   */
  GLTFParser.prototype.loadScene = (function() {
    // scene node hierachy builder

    function buildNodeHierachy(nodeId, parentObject, json, parser) {
      var nodeDef = json.nodes[nodeId];

      return parser
        .getDependency("node", nodeId)
        .then(function(node) {
          if (nodeDef.skin === undefined) return node;

          // build skeleton here as well

          var skinEntry;

          return parser
            .getDependency("skin", nodeDef.skin)
            .then(function(skin) {
              skinEntry = skin;

              var pendingJoints = [];

              for (var i = 0, il = skinEntry.joints.length; i < il; i++) {
                pendingJoints.push(
                  parser.getDependency("node", skinEntry.joints[i])
                );
              }

              return Promise.all(pendingJoints);
            })
            .then(function(jointNodes) {
              node.traverse(function(mesh) {
                if (!mesh.isMesh) return;

                var bones = [];
                var boneInverses = [];

                for (var j = 0, jl = jointNodes.length; j < jl; j++) {
                  var jointNode = jointNodes[j];

                  if (jointNode) {
                    bones.push(jointNode);

                    var mat = new THREE.Matrix4();

                    if (skinEntry.inverseBindMatrices !== undefined) {
                      mat.fromArray(
                        skinEntry.inverseBindMatrices.array,
                        j * 16
                      );
                    }

                    boneInverses.push(mat);
                  } else {
                    console.warn(
                      'THREE.GLTFLoader: Joint "%s" could not be found.',
                      skinEntry.joints[j]
                    );
                  }
                }

                mesh.bind(
                  new THREE.Skeleton(bones, boneInverses),
                  mesh.matrixWorld
                );
              });

              return node;
            });
        })
        .then(function(node) {
          // build node hierachy

          parentObject.add(node);

          var pending = [];

          if (nodeDef.children) {
            var children = nodeDef.children;

            for (var i = 0, il = children.length; i < il; i++) {
              var child = children[i];
              pending.push(buildNodeHierachy(child, node, json, parser));
            }
          }

          return Promise.all(pending);
        });
    }

    return function loadScene(sceneIndex) {
      var json = this.json;
      var extensions = this.extensions;
      var sceneDef = this.json.scenes[sceneIndex];
      var parser = this;

      // Loader returns Group, not Scene.
      // See: https://github.com/mrdoob/three.js/issues/18342#issuecomment-578981172
      var scene = new THREE.Group();
      if (sceneDef.name) scene.name = parser.createUniqueName(sceneDef.name);

      assignExtrasToUserData(scene, sceneDef);

      if (sceneDef.extensions)
        addUnknownExtensionsToUserData(extensions, scene, sceneDef);

      var nodeIds = sceneDef.nodes || [];

      var pending = [];

      for (var i = 0, il = nodeIds.length; i < il; i++) {
        pending.push(buildNodeHierachy(nodeIds[i], scene, json, parser));
      }

      return Promise.all(pending).then(function() {
        return scene;
      });
    };
  })();

  return GLTFLoader;
})();
